A first solution relates to the video cameras on board a terrestrial, naval or aerial platform which are in general mounted on an orientable mount, for example of the theodolite type, or else in a sighting instrument having a mirror with two orientable axes. Servocontrols ensure stabilization of the line of sight by utilizing the information from a gyroscope or from rate gyros secured to the camera.
Another solution concerns portable lightweight cameras of the camcorder or binocular type (intensified or infrared) which are oriented and stabilized manually by the observer but remain subject to the residual erratic movements of the latter. Solutions for stabilizing the line of sight of the camera are implemented by associating two gyrometric sensors secured to the casing of the camera with an opto-mechanical deviator component such as a variable-angle prism or lens off-centered by actuators included in the objective of the camera.
In these two cases, one speaks of “a priori” stabilization.
Other solutions call upon image processing for mutual registration of the successive images of a video sequence. In this case, one speaks of “a posteriori” electronic stabilization. An example of a posteriori stabilization is described in patent FR 2 828 315: low-frequency images are extracted from the images acquired and are used to determine by an optical flow procedure the translations and rotations to be applied to the images so as to stabilize them. “A posteriori” electronic stabilization procedures are not usable in the case of images exhibiting a uniform background structure or a repetitive texture (sky, forest or maritime surface for example).